AUTHOR=Zając Magdalena , Sztromwasser Paweł , Bortolaia Valeria , Leekitcharoenphon Pimlapas , Cavaco Lina M. , Ziȩtek-Barszcz Anna , Hendriksen Rene S. , Wasyl Dariusz 

TITLE=Occurrence and Characterization of mcr-1-Positive Escherichia coli Isolated From Food-Producing Animals in Poland, 2011–2016

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01753

DOI=10.3389/fmicb.2019.01753

ISSN=1664-302X

ABSTRACT=<p>The emergence of plasmid-mediated colistin resistance (<italic>mcr</italic> genes) threatens the effectiveness of polymyxins, which are last-resort drugs to treat infections by multidrug- and carbapenem-resistant Gram-negative bacteria. Based on the occurrence of colistin resistance the aims of the study were to determine possible resistance mechanisms and then characterize the <italic>mcr</italic>-positive <italic>Escherichia coli</italic>. The research used material from the Polish national and EU harmonized antimicrobial resistance (AMR) monitoring programs. A total of 5,878 commensal <italic>E. coli</italic> from fecal samples of turkeys, chickens, pigs, and cattle collected in 2011–2016 were screened by minimum inhibitory concentration (MIC) determination for the presence of resistance to colistin (R) defined as <italic>R</italic> &gt; 2 mg/L. Strains with MIC = 2 mg/L isolated in 2014–2016 were also included. A total of 128 isolates were obtained, and most (66.3%) had colistin MIC of 2 mg/L. PCR revealed <italic>mcr-1</italic> in 80 (62.5%) isolates recovered from 61 turkeys, 11 broilers, 2 laying hens, 1 pig, and 1 bovine. No other <italic>mcr</italic>-type genes (including <italic>mcr-2</italic> to -<italic>5</italic>) were detected. Whole-genome sequencing (WGS) of the <italic>mcr-1</italic>–positive isolates showed high diversity in the multi-locus sequence types (MLST) of <italic>E. coli</italic>, plasmid replicons, and AMR and virulence genes. Generally <italic>mcr-1.1</italic> was detected on the same contig as the IncX4 (76.3%) and IncHI2 (6.3%) replicons. One isolate harbored <italic>mcr-1</italic>.<italic>1</italic> on the chromosome. Various extended-spectrum beta-lactamase (<italic>bla</italic><sub><italic>SHV</italic>–12</sub>, <italic>bla</italic><sub><italic>CTX</italic>–<italic>M</italic>–1</sub>, <italic>bla</italic><sub><italic>CTX</italic>–<italic>M</italic>–15</sub>, <italic>bla</italic><sub><italic>TEM</italic>–30</sub>, <italic>bla</italic><sub><italic>TEM</italic>–52</sub>, and <italic>bla</italic><sub><italic>TEM</italic>–135</sub>) and quinolone resistance genes (<italic>qnrS1</italic>, <italic>qnrB19</italic>, and chromosomal <italic>gyrA, parC</italic>, and <italic>parE</italic> mutations) were present in the <italic>mcr-1</italic>.<italic>1</italic>–positive <italic>E. coli</italic>. A total of 49 sequence types (ST) were identified, ST354, ST359, ST48, and ST617 predominating. One isolate, identified as ST189, belonged to atypical enteropathogenic <italic>E. coli.</italic> Our findings show that <italic>mcr-1</italic>.<italic>1</italic> has spread widely among production animals in Poland, particularly in turkeys and appears to be transferable mainly by IncX4 and IncHI2 plasmids spread across diverse <italic>E. coli</italic> lineages. Interestingly, most of these <italic>mcr-1</italic>–positive <italic>E. coli</italic> would remain undetected using phenotypic methods with the current epidemiological cut-off value (ECOFF). The appearance and spread of <italic>mcr-1</italic> among various animals, but notably in turkeys, might be considered a food chain, and public health hazard.</p>